This article for pupils and teachers looks at a number that even the great mathematician, Pythagoras, found terrifying.

Read all about Pythagoras' mathematical discoveries in this article written for students.

If the yellow equilateral triangle is taken as the unit for area, what size is the hole ?

Using the interactivity, can you make a regular hexagon from yellow triangles the same size as a regular hexagon made from green triangles ?

How many differently shaped rectangles can you build using these equilateral and isosceles triangles? Can you make a square?

The number 2.525252525252.... can be written as a fraction. What is the sum of the denominator and numerator?

What fractions can you find between the square roots of 65 and 67?

An introduction to proof by contradiction, a powerful method of mathematical proof.

Ranging from kindergarten mathematics to the fringe of research this informal article paints the big picture of number in a non technical way suitable for primary teachers and older students.